In an ultra-large scale integrated (ULSI) circuit, there may be transistors operating with various threshold voltages and gate oxide thicknesses. In order to achieve such a circuit with transistors operating at various threshold voltages and having different gate oxide thicknesses, manufacturing process conditions are adjusted. Various device parameters may be adjusted by the adjustment of the process conditions. These include halo implant and oxidation recipes.
One of the concerns with such a methodology to achieve a circuit with a plurality of transistors operating at various threshold voltages is the manufacturing complexity required to achieve such a circuit. The implants and oxidation recipes that are developed must be properly controlled with several lithography reticles.